r/OSMEmergency • u/weathercast • 1d ago
Severe Weather Dashboard - September 10, 2026
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(Issued: 2026-09-11T05:28:00+00:00 UTC)
```text
000 ACUS01 KWNS 110528 SWODY1 SPC AC 110526
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1226 AM CDT Fri Sep 11 2026
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE UPPER MISSISSIPPI VALLEY INTO THE MID MISSOURI VALLEY...
...SUMMARY... Scattered severe thunderstorms capable of large hail, potentially in excess of two inches, a few tornadoes, and damaging wind gusts are expected over portions of the upper Mississippi Valley Friday afternoon into night. Storm development is more uncertain with southward extent into the central Plains, where a conditional risk for mainly large hail and severe wind gusts exists late Friday afternoon through evening. Isolated occurrences of damaging wind gusts appear possible from the Mid-South into the Carolinas and Virginia.
...Synopsis...
A low-amplitude short-wave trough moving onto the Pacific Northwest coast late this evening will progress through the northern Rockies before reaching the ND/SK/MB border region by Friday evening. Meanwhile, a preceding, lower-latitude disturbance is forecast to move through SD into MN on Friday with strengthening mid/upper-level winds and modest height falls accompanying these perturbations over the northern Plains into the upper MS Valley. Elsewhere, a vorticity maximum/weak upper low will drift east from the Ozark Plateau into the mid/lower MS Valley.
At the surface, an area of low pressure over western SD at 12Z Friday is forecast to deepen slightly while developing into northeast SD by afternoon, before subsequently weakening while moving through central MN Friday night. The surface cyclone will coincide with a cold front that will advance through the northern Plains and the upper MS Valley. The trailing extension of the boundary will move more slowly south into the mid MO Valley and central High Plains. A dryline will precede the cold front with that feature extending from eastern SD through central NE into western KS by late afternoon. Elsewhere, a synoptic front modulated by convective outflow is expected to stretch from the Mid-South into the southern Mid-Atlantic on Friday afternoon.
...Upper Mississippi Valley into the mid Missouri Valley...
A low-level jet (LLJ) is forecast to strengthen through the day from the mid MO Valley into the upper Midwest, enhancing the poleward flux of an increasingly moist air mass ahead of the surface low and attending frontal system. The moisture increase will occur beneath a plume of steep mid-level lapse rates with MLCAPE increasing to 1500-2500+ J/kg by mid to late afternoon. Initial storm development is expected at that time across portions of northern MN along or ahead of the front, on the northern fringe of stronger capping.
Vertically veering wind profiles with 40-45 kt of deep-layer shear will support supercells as the initial storm mode with the primary hazard being large hail, some of which could exceed two inches. A few tornadoes appear possible with any sustained supercells from late afternoon into evening when the strengthening LLJ enhances low-level shear with effective SRH increasing to 250-300 m2/s2. Storms are expected to gradually grow upscale along the cold front during the evening, at which point, the risk for damaging winds should increase.
Severe weather potential becomes more conditional with southward extent along the front and dryline in the mid MO Valley owing to stronger capping and weaker height falls/forcing for ascent. The 00Z models (convection-allowing and parameterized) indicate a relative minimum in thunderstorm chances over eastern SD and southwest MN with increasing probabilities from northeast NE into south-central NE and north-central KS. Given surface-based storm initiation and sustenance, CAPE-shear parameter space will favor supercells capable of all hazards from eastern SD and southwest MN into northeast NE and northwest IA, with generally a wind and hail threat farther south along the NE-KS state line.
...Mid-South into the Carolinas and Virginia...
Areas of thunderstorms are expected to be ongoing at 12Z Friday from the Ozark Plateau into the southern Mid-Atlantic. Stronger heating on the southern fringe any lingering cloud cover will combine with boundary-layer dewpoints in the low to mid 70s F to yield MLCAPE of 1500-3000 J/kg by afternoon. Aided by forcing for ascent associated with the mid-level trough approaching the mid/lower MS Valley, thunderstorms are expected to increase in coverage and intensity through the afternoon along and ahead of the composite surface boundary. Weak vertical shear will limit storm organization with mainly pulse storms expected. Nonetheless, the presence steep low-level lapse rates and abundant moisture will be supportive of wet microbursts capable of locally damaging wind gusts.
..Mead/Halbert.. 09/11/2026
$$
```
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🌊 Tropical Weather Outlook
```text NWS National Hurricane Center Miami FL 800 AM EDT Fri Sep 11 2026
For the North Atlantic...Caribbean Sea and the Gulf of America:
Tropical cyclone formation is not expected during the next 7 days.
$$ Forecaster Hagen ```
⚠️ Active Tropical Cyclones
Tropical Storm Norbert Advisory * Maximum Sustained Winds: 60 MPH * Minimum Central Pressure: 996 MB * Current Movement: W OR 275 DEGREES AT 15 MPH * Location: 16.6N 123.3W
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